Trends in blood mercury concentrations and fish consumption among U.S. women of reproductive age, NHANES, 1999-2010

Trends of hair Hg accumulation in reproductive-age women living in Central Russia and the calculated costs of Hg-induced IQ loss in the period between 2005 and 2021

The objective of the present study was to retrospectively evaluate hair mercury (Hg) content in reproductive-age women living in Central Russia (Moscow and Moscow region), and to calculate the potential costs of the potential Hg-induced IQ loss in a hypothetical national birth cohort.

MATERIALS AND METHODS

A total of 36,263 occupationally non-exposed women aged between 20 and 40 years living in Moscow (n = 30,626) or Moscow region (n = 5637) in the period between 2005 and 2021 participated in this study. Hair Hg content was evaluated with inductively coupled plasma-mass spectrometry (ICP-MS). Hair Hg levels in reproductive-age women were used for assessment of the potential IQ loss and its costs.

RESULTS

The results demonstrate that hair Hg content in the periods between 2010 and 2015, and 2016-2021 was significantly lower than that in 2005-2009 by 26 % and 51 %, respectively. The highest hair Hg level was observed in women in 2005 (0.855 µg/g), being more than 2.5-fold higher than the lowest value observed in 2020 (0.328 µg/g). Multiple regression analysis revealed a significant inverse association between the year of analysis and hair Hg content (β = -0.288; p < 0.001). The calculations demonstrate that in 2005 the costs of IQ loss in children exceeded 1.0 (1.6) billion USD, whereas in 2020 the costs of IQ loss accounted to approximately 0.15 (0.28) billion USD.

CONCLUSION

Taken together, our data demonstrate that Hg accumulation in reproductive-age women reduced significantly in Russia from 2005 to 2021 resulting in predicted economic benefits by decreasing the costs of Hg-induced IQ loss.

Infantile allergic diseases: a cohort study prenatal fish intake and mercury exposure context

BACKGROUND

Allergic diseases (ADs) have been increasingly reported in infants and children over the last decade. Diet, especially the inclusion of fish intake, may help to lower the risk of ADs. However, fish also, can bioaccumulate environmental contaminants such as mercury. Hence, our study aims to determine what effects the type and frequency of fish intake have on ADs in six-month-old infants, independently and jointly with mercury exposure.

METHODS

This study is part of the prospective birth cohort: Mothers and Children's Environmental Health (MOCEH) study in South Korea. Data was collected on prenatal fish intake, prenatal mercury concentration and ADs for infants aged six months for 590 eligible mother-infant pairs. Logistic regression analysis was conducted to evaluate the risk of prenatal fish intake and mercury concentration on ADs in infants. Finally, interaction between fish intake and mercury concentration affecting ADs in infants was evaluated. Hazard ratios of prenatal fish intake on ADs in 6 month old infants were calculated by prenatal mercury exposure.

RESULTS

Logistic regression analysis showed that white fish (OR: 0.53; 95% CI 0.30-0.94; P < 0.05) intake frequency, once a week significantly decreased the risk of ADs in infants. Stratification analysis showed that consuming white fish once a week significantly reduced the hazard of ADs (HR: 0.44; 95% CI 0.21-0.92; P < 0.05) in infants in the high-mercury (≥ 50th percentile) exposure group.

CONCLUSION

The result indicates that prenatal white fish intake at least once a week reduces the risk of ADs in infants, especially in the group with high prenatal mercury exposure.

Characterizing Chemical Exposure Trends from NHANES Urinary Biomonitoring Data

BACKGROUND

Xenobiotic metabolites are widely present in human urine and can indicate recent exposure to environmental chemicals. Proper inference of which chemicals contribute to these metabolites can inform human exposure and risk. Furthermore, longitudinal biomonitoring studies provide insight into how chemical exposures change over time.

OBJECTIVES

We constructed an exposure landscape for as many human-exposure relevant chemicals over as large a time span as possible to characterize exposure trends across demographic groups and chemical types.

METHODS

We analyzed urine data of nine 2-y cohorts (1999-2016) from the National Health and Nutrition Examination Survey (NHANES). Chemical daily intake rates (in milligrams per kilogram bodyweight per day) were inferred, using the R package bayesmarker, from metabolite concentrations in each cohort individually to identify exposure trends. Trends for metabolites and parents were clustered to find chemicals with similar exposure patterns. Exposure variation by age, gender, and body mass index were also assessed.

RESULTS

Intake rates for 179 parent chemicals were inferred from 151 metabolites (96 measured in five or more cohorts). Seventeen metabolites and 44 parent chemicals exhibited fold-changes ≥ 10 between any two cohorts (deltamethrin, di-n -octyl phthalate, and di-isononyl phthalate had the greatest exposure increases). Di-2-ethylhexyl phthalate intake began decreasing in 2007, whereas both di-isobutyl and di-isononyl phthalate began increasing shortly before. Intake for four parabens was markedly higher in females, especially reproductive-age females, compared with males and children. Cadmium and arsenobetaine exhibited higher exposure for individuals > 65 years of age and lower for individuals < 20 years of age.

DISCUSSION

With appropriate analysis, NHANES indicates trends in chemical exposures over the past two decades. Decreases in exposure are observable as the result of regulatory action, with some being accompanied by increases in replacement chemicals. Age- and gender-specific variations in exposure were observed for multiple chemicals. Continued estimation of demographic-specific exposures is needed to both monitor and identify potential vulnerable populations. https://doi.org/10.1289/EHP12188.

Addressing Uncertainties in Potential Human Dietary Exposure to Mercury in the Watershed of the South River, Virginia, USA

Much has been published about the harmful effects to humans when they are exposed to mercury (Hg) in environmental media including their diet. Numerous health advisories around the world, including for the South River, Virginia, USA, warn against consumption of Hg-contaminated fish species. Fewer studies have focused on other dietary sources of Hg and how to advise humans potentially exposed by this route. In undertaking a human health risk assessment for the former DuPont facility in Waynesboro, Virginia, USA, and the nearby South River and surrounding watershed, the available published information on Hg exposure through dietary consumption of nonfish items proved unsuitable for extrapolation purposes. In response, an evaluation of potential Hg exposure to residents who might consume livestock, poultry, and wildlife raised or collected in the South River watershed was conducted to inform the risk-assessment process. The newly collected data on Hg in these dietary items filled an important data gap, suggesting that there was little concern about limiting dietary consumption for most items. These results were communicated to the public through print and electronic platforms, in the form of "fact sheets." We describe the studies and actions taken to better explain the potential for human exposures to Hg in nonfish dietary items from a portion of the watershed of the South River. Environ Toxicol Chem 2023;42:2237-2252. © 2023 SETAC.

Sociodemographic Disparities in Mercury Exposure from United States Coal-Fired Power Plants

Hazardous air pollutants emitted by United States (U.S) coal-fired power plants have been controlled by the Mercury and Air Toxics Standards (MATS) since 2012. Sociodemographic disparities in traditional air pollutant exposures from U.S. power plants are known to occur but have not been evaluated for mercury (Hg), a neurotoxicant that bioaccumulates in food webs. Atmospheric Hg deposition from domestic power plants decreased by 91% across the contiguous U.S. from 6.4 Mg in 2010 to 0.55 Mg in 2020. Prior to MATS, populations living within 5 km of power plants (n = 507) included greater proportions of frequent fish consumers, individuals with low annual income and less than a high school education, and limited English-proficiency households compared to the US general population. These results reinforce a lack of distributional justice in plant siting found in prior work. Significantly greater proportions of low-income individuals lived within 5 km of active facilities in 2020 (n = 277) compared to plants that retired after 2010, suggesting that socioeconomic status may have played a role in retirement. Despite large deposition declines, an end-member scenario for remaining exposures from the largest active power plants for individuals consuming self-caught fish suggests they could still exceed the U.S. Environmental Protection Agency reference dose for methylmercury.

The association of lead exposure with blood pressure and hypertension: a mediation analyses of estimated glomerular filtration rate

The link between lead and blood pressure was debatable, and whether it was mediated by renal function was unknown. The purpose was to investigate the relationship between blood lead concentrations and blood pressure and hypertension, as well as the mediating role of estimated glomerular filtration rate (eGFR) in this relationship. Participants aged 18 were recruited from the National Health and Nutrition Examination Survey (1999-2014) and provided with lead and blood pressure data. Multivariate linear and logistic regression, stratification, interaction tests, and a restricted cubic spline curve were used to assess the association of blood lead with systolic/diastolic blood pressure (SBP/DBP) and hypertension, and mediation effect analysis was used to investigate the role of eGFR in this relationship. A total of 20,073 subjects were enrolled, and among them, 9837 (49.01%) were male and 7800 (38.86%) were hypertensive patients. Multivariate linear and logistic regression analysis showed that blood lead levels were significantly associated with SBP (β = 3.14, 95%CI: 2.03, 4.25; P < 0.001), DBP (β = 3.50, 95%CI: 2.69, 4.30; P < 0.001), and hypertension (OR = 1.29, 95%CI: 1.09, 1.52; P = 0.0026). In comparison to the lowest blood lead quartile, the highest lead group was significantly associated with SBP (= 2.55, 95%CI: 1.66, 3.44; P = 0.0001), DBP (= 2.60, 95%CI: 1.95, 3.24; P = 0.0001), and hypertension (OR = 1.26, 95%CI: 1.10, 1.45; P = 0.0007). Mediation analysis showed that the proportion of blood lead mediated for SBP, DBP, and hypertension was 3.56% (95%CI: 0.42%, 7.96%; P = 0.0320), 6.21% (95%CI: 4.02%, 9.32%; P < 0.0001), and 17.39% (95%CI: 9.34%, 42.71%; P < 0.0001), respectively. Adjusted restricted cubic spline curves presented a non-linear correlation of blood lead levels with DBP (P-non-linearity < 0.001), linear with SBP (P-non-linearity = 0.203), and hypertension (P-non-linearity = 0.763). Our findings demonstrated that blood lead levels were non-linear with DBP, but linear with SBP and hypertension, and this relationship was mediated by eGFR.

Effects of mercury exposure on fetal body burden and its association with infant growth

Several studies have been conducted among South Korean to investigate effects of high blood mercury (Hg) levels. In this study fetal body burden of Hg in 344 pregnant women were estimated using a physiologically-based pharmacokinetic model (PBPK) and its associative effects on the growth of infants were analyzed. The association between cord blood Hg and growth variables at birth was analyzed based on parameters such as the sex of the newborn, living area, maternal age group, gestation day, maternal body mass index . We investigated the effects of Hg on infant growth through follow-ups, using a non-linear mixed model. The mean Hg levels in maternal and cord blood were 4.47 μg/L and 7.35 μg/L, respectively. Among the subjects, the corresponding fetal body burden for Methylmercury ranged between 26.3-86.9 mg. Cord blood Hg levels positively correlated with length at birth. Furthermore, the high cord blood group showed greater growth rates compared to the low cord blood group. Therefore, we suggest that pregnant women should make efforts to mitigate exposures to Hg, specifically from diet. Further research is suggested to investigate the relationship between the follow-up growth of the infants and Hg levels, considering fish consumption, diet information, and other environmental pollutants.

Mercury Induced Tissue Damage, Redox Metabolism, Ion Transport, Apoptosis, and Intestinal Microbiota Change in Red Swamp Crayfish (Procambarus clarkii): Application of Multi-Omics Analysis in Risk Assessment of Hg

As one of the most toxic elements, mercury (Hg) is a widespread toxicant in aquatic environments. Crayfish are considered suitable for indicating the impact of heavy metals on aquatic crustaceans. Nevertheless, Hg toxicity on Procambarus clarkii is largely unknown. In this research, the acute Hg-induced alterations of biochemical responses, histopathology, hepatopancreatic transcriptome, and intestinal microbiome of Procambarus clarkii were studied. Firstly, Hg induced significant changes in reactive oxygen species (ROS) and malonaldehyde (MDA) content as well as antioxidant enzyme activity. Secondly, Hg exposure caused structural damage to the hepatopancreas (e.g., vacuolization of the epithelium and dilatation of the lumen) as well as to the intestines (e.g., dysregulation of lamina epithelialises and extension of lamina proprias). Thirdly, after treatment with three different concentrations of Hg, RNA-seq assays of the hepatopancreas revealed a large number of differentially expressed genes (DEGs) linked to a specific function. Among the DEGs, a lot of redox metabolism- (e.g., ACOX3, SMOX, GPX3, GLO1, and P4HA1), ion transport- (e.g., MICU3, MCTP, PYX, STEAP3, and SLC30A2), drug metabolism- (e.g., HSP70, HSP90A, CYP2L1, and CYP9E2), immune response- (e.g., SMAD4, HDAC1, and DUOX), and apoptosis-related genes (e.g., CTSL, CASP7, and BIRC2) were identified, which suggests that Hg exposure may perturb the redox equilibrium, disrupt the ion homeostasis, weaken immune response and ability, and cause apoptosis. Fourthly, bacterial 16S rRNA gene sequencing showed that Hg exposure decreased bacterial diversity and dysregulated intestinal microbiome composition. At the phylum level, there was a marked decrease in Proteobacteria and an increase in Firmicutes after exposure to high levels of Hg. With regards to genus, abundances of Bacteroides, Dysgonomonas, and Arcobacter were markedly dysregulated after Hg exposures. Our findings elucidate the mechanisms involved in Hg-mediated toxicity in aquatic crustaceans at the tissue, cellular, molecular as well as microbial levels.

Long-term monitoring of mercury in young German adults: Time trend analyses from the German Environmental Specimen Bank, 1995-2018

As highlighted in the Minamata Convention, Mercury (Hg) in its various forms poses a substantial risk to human health and the environment. The health relevance of Hg is also recognized by the European Human Biomonitoring Initiative (HBM4EU), which classifies Hg as a priority substance, since considerable knowledge and data gaps on Hg exposure levels and their changes over time still exist in Europe. The German Environmental Specimen Bank (German ESB) provides valuable policy relevant data and long-term trends of substance exposure on a national level for international comparison and evaluation. In this study we analysed data of the German ESB on Hg exposure of young adults aged 20 to 29 including data on urinary Hg levels from 1995 to 2018 and whole blood Hg levels from 2001 to 2010. Results show a clear decrease in both, about 86% in urine total daily Hg excretion from 1995 (0.76 μg/L) to 2018 (0.11 μg/L) (n = 10,069) and about 57% in blood concentrations of Hg from 2001 (1.76 μg/L) to 2010 (0.77 μg/L) (n = 4085). Over the investigated timeframe only a few values exceeded the toxicologically derived health based guidance value HBM I for blood and urine, with these exceedances decreasing over time in line with the general trend. The factors mostly influencing Hg excretion identified in this study are dental amalgam as well as fish and seafood consumption. Besides other factors (e.g. age and sex), also airborne Hg exposure appears to be a low but evident influencing factor in Germany. Although a considerable decrease in internal Hg exposure is recognized in the last decades, the current low-level exposure may cause adverse health effects especially to vulnerable groups such as pregnant women and children. To further elucidate and evaluate current exposure sources and to reduce human exposure to Hg, continuous environmental and human biomonitoring is needed.

Association of Seafood Consumption and Mercury Exposure With Cardiovascular and All-Cause Mortality Among US Adults

IMPORTANCE

Although seafood is known to contain heart-healthy omega-3 fatty acids, many people choose to limit their seafood consumption because of fear of mercury exposure from seafood. It is imperative to clarify the potential health effects of current mercury exposure in contemporary populations.

OBJECTIVE

To examine the association of seafood consumption and mercury exposure with all-cause and cardiovascular disease (CVD)-related mortality in the US general population.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study included adults 20 years or older who participated in the 2003 to 2012 cycles of the National Health and Nutrition Examination Survey; data were linked to mortality records through December 31, 2015. Data analysis was performed from January to March 10, 2021.

EXPOSURES

Seafood consumption was assessed through two 24-hour dietary recalls, and mercury exposure was assessed by blood mercury levels.

MAIN OUTCOMES AND MEASURES

All-cause and CVD-related mortality. Multivariable Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% CIs of mortality associated with usual seafood consumption and blood mercury concentration quartiles.

RESULTS

This study included 17 294 participants (mean [SD] age, 45.9 [17.1] years; 9217 [53.3%] female) with a mean (SD) blood mercury concentration of 1.62 (2.46) μg/L. During 131 276 person-years of follow-up, 1076 deaths occurred, including 181 deaths from CVD. The multivariable-adjusted HR for an increase in seafood consumption of 1 oz equivalent per day and all-cause mortality was 0.84 (95% CI, 0.66-1.07) and for CVD-related mortality was 0.89 (95% CI, 0.54-1.47). Blood mercury level was not associated with all-cause or CVD-related mortality. Comparing the highest with the lowest quartile of blood mercury concentration, the multivariable-adjusted HRs were 0.82 (95% CI, 0.66-1.05) for all-cause mortality and 0.90 (95% CI, 0.53-1.52) for CVD-related mortality.

CONCLUSIONS AND RELEVANCE

In this cohort study of US adults, seafood consumption and mercury exposure with the current seafood consumption level were not significantly associated with the risk of all-cause or CVD-related mortality. These findings may inform future public health guidelines regarding mercury exposure, seafood consumption, and cardiovascular health promotion.

Assessment of Lead and Mercury Exposure Levels in the General Population of Korea Using Integrated National Biomonitoring Data

In Korea, the estimated values of blood lead (Pb) and mercury (Hg) levels differ between two national-level biomonitors, namely the Korean National Environmental Health Survey and the Korea National Health and Nutrition Examination Survey. The present study used integrated data from these surveys to estimate the representative values of the change in concentration and recent distribution characteristics. The yearly trend of age-standardized exposure levels in regular adults was identified, and the geometric mean (GM) adjusted according to demographic characteristics was presented. Age-standardized GM for blood Pb and Hg in the integrated data was 2.06 and 3.64 μg/L in 2008, respectively, which decreased to 1.55 and 2.92 μg/L, respectively, by 2017. Adjusted GMs from most recently conducted surveys (2015-2017) were 1.61 and 2.98 μg/L for blood Pb and Hg, respectively. In particular, the adjusted percentage of blood Hg exceeding the reference value of 5 μg/L was 20.79%. While the blood Pb and Hg exposure levels are decreasing in Korea, the levels remain high relative to those in other countries. The Hg levels exceeded the reference value in many individuals. Therefore, continued biomonitoring must be conducted, and a reduction plan and exposure management are needed for harmful metals, including Hg.

Optimization of a Digestion Method to Determine Total Mercury in Fish Tissue by Cold Vapor Atomic Fluorescence Spectrophotometry

Several microwave-assisted digestion methods were tested at the Centro de Estudios Aplicados en Química laboratory in Quito, Ecuador, to determine the accuracy and performance efficiency of the mineralization process for the determination of total mercury in fish tissue by cold vapor atomic fluorescence spectrophotometry. The use of MARSEasyPrep high-pressure vessels, low amounts of reagents (1 cm³ HNO₃, 1 cm³ H₂O₂, and 1 cm³ HClO₄), an irradiation temperature of 210 °C, and 35 min of mineralization time resulted in accurate performance, with recoveries of certified reference material DORM-4 between 90.1% and 105.8%. This is better than the Association of Official Analytical Chemists 2015.01 method, which has a reported accuracy of 81%. The repeatability precision and intermediate precision were established at three concentration levels (0.167, 0.500, and 0.833 mg·kg⁻¹) and expressed as the percentage of the relative standard deviation ranging from 1.5% to 3.0% and 1.7% to 4.2%, respectively. Further, the method was satisfactorily applied to analyze fortified samples of tilapia (Oreochromis niloticus), with recoveries ranging from 98.3% to 104.3%. The instrumental limits of detection and quantification were 0.118 µg·dm⁻³ and 0.394 µg·dm⁻³, respectively.

Seafood, wine, rice, vegetables, and other food items associated with mercury biomarkers among seafood and non-seafood consumers: NHANES 2011-2012

Fish/seafood consumption is a source of mercury; other dietary sources are not well described. This cross-sectional study used National Health and Nutrition Examination Survey (NHANES) 2011-2012 data. Participants self-reported consuming fish/seafood (N = 5427) or not (N = 1770) within the past 30 days. Whole blood total mercury (THg), methylmercury (MeHg), and urinary mercury (UHg) were determined. Diet was assessed using 24 h recall. Adjusted regression models predicted mercury biomarker concentrations with recent food consumption, while controlling for age, sex, education, and race/ethnicity. Geometric mean THg was 0.89 µg/L (95% confidence interval (CI): 0.78, 1.02) (seafood consumers) and 0.31 µg/L (95% CI: 0.28, 0.34) (non-seafood consumers); MeHg and UHg concentrations follow similar patterns. In adjusted regressions among seafood consumers, significant associations were observed between mercury biomarkers with multiple foods, including fish/seafood, wine, rice, vegetables/vegetable oil, liquor, and beans/nuts/soy. Among non-seafood consumers, higher THg was significantly associated with mixed rice dishes, vegetables/vegetable oil, liquor, and approached statistical significance with wine (p < 0.10); higher MeHg was significantly associated with wine and higher UHg was significantly associated with mixed rice dishes. Fish/seafood consumption is the strongest dietary predictor of mercury biomarker concentrations; however, consumption of wine, rice, vegetables/vegetable oil, or liquor may also contribute, especially among non-seafood consumers.

Association of Blood Mercury Level with the Risk of Depression According to Fish Intake Level in the General Korean Population: Findings from the Korean National Health and Nutrition Examination Survey (KNHANES) 2008-2013

Mercury is a cumulative neurotoxic agent, exposure to high levels of which may increase the risk of psychiatric symptoms. The purpose of this study was to examine the associations between blood mercury and depression risk in Korean adults. We analyzed the Korean National Health and Nutrition Examination Survey (KNHANES) with 11,754 participants (male: 5834 female: 5920) aged ≥19 years from 2008 to 2013. The associations of blood mercury with risk of depression were estimated using multivariate logistic regression after adjustment for potential confounders. We found a significantly increased risk of depression in the highest quintile for blood mercury (multivariate OR = 2.05; 95% CI = 1.20-3.48; P trend = 0.03) among female, but not male. A stratification analysis by fish intake showed that the association between depression and blood mercury was strengthened (OR = 4.00; 95% CI = 1.51-10.6; P trend = 0.015) among females with the lowest tertile of fish intake. The results of this study suggest that higher levels of blood mercury, especially in cases of lower fish intake, are positively associated with the risk of depression in Korean women.

Best Practices for Conducting and Interpreting Studies to Validate Self-Report Dietary Assessment Methods

Careful consideration of the validity and reliability of methods intended to assess dietary intake is central to the robustness of nutrition research. A dietary assessment method with high validity is capable of providing useful measurement for a given purpose and context. More specifically, a method with high validity is well grounded in theory; its performance is consistent with that theory; and it is precise, dependable, and accurate within specified performance standards. Assessing the extent to which dietary assessment methods possess these characteristics can be difficult due to the complexity of dietary intake, as well as difficulties capturing true intake. We identified challenges and best practices related to the validation of self-report dietary assessment methods. The term validation is used to encompass various dimensions that must be assessed and considered to determine whether a given method is suitable for a specific purpose. Evidence on the varied concepts of validity and reliability should be interpreted in combination to inform judgments about the suitability of a method for a specified purpose. Self-report methods are the focus because they are used in most studies seeking to measure dietary intake. Biomarkers are important reference measures to validate self-report methods and are also discussed. A checklist is proposed to contribute to strengthening the literature on the validation of dietary assessment methods and ultimately, the nutrition literature more broadly.

Using Birth Cohort Data to Estimate Prenatal Chemical Exposures for All Births around the New Bedford Harbor Superfund Site in Massachusetts

BACKGROUND

Children born near New Bedford, Massachusetts, have been prenatally exposed to multiple environmental chemicals, in part due to an older housing stock, maternal diet, and proximity to the New Bedford Harbor (NBH) Superfund site. Chemical exposure measures are not available for all births, limiting epidemiologic investigations and potential interventions.

OBJECTIVE

We linked biomonitoring data from the New Bedford Cohort (NBC) and birth record data to predict prenatal exposures for all contemporaneous area births.

METHODS

We used prenatal exposure biomarker data from the NBC, a population-based cohort of 788 mother-infant pairs born during 1993–1998 to mothers living near the NBH, linked to their corresponding Massachusetts birth record data, to build predictive models for cord serum polychlorinated biphenyls (expressed as a sum, [Formula: see text]), [Formula: see text] (DDE), hexachlorobenzene (HCB), cord blood lead (Pb), and maternal hair mercury (Hg). We applied the best fit models (highest pseudo [Formula: see text]), with multivariable smooths of continuous variables, to predict exposure biomarkers for all 10,270 births during 1993–1998 around the NBH. We used 10-fold cross validation to validate the exposure models and the bootstrap method to characterize sampling variability in the exposure predictions.

RESULTS

The 10-fold cross-validated [Formula: see text] for the [Formula: see text], DDE, HCB, Pb, and Hg exposure models were 0.54, 0.40, 0.34, 0.46, and 0.40, respectively. For each exposure model, multivariable smooths of continuous variables improved the fit compared with linear models. Other variables with significant effects on exposure estimates were paternal education, maternal race/ethnicity, and maternal ancestry. The resulting exposure predictions for all births had variability consistent with the NBC measured exposures.

CONCLUSIONS

Predictive models using multivariable smoothing explained reasonable amounts of variance in prenatal exposure biomarkers. Our analyses suggest that prenatal chemical exposures can be predicted for all contemporaneous births in the same geographic area by modeling available biomarker data for a subset of that population. https://doi.org/10.1289/EHP4849.

The protective role of ascorbic acid in the hepatotoxicity of cadmium and mercury in rabbits

The liver is one of the vital and sensitive organs which are usually exposed against the toxicity of mercury (Hg) and cadmium (Cd). The main objective of the current study was to evaluate the potential toxicological effects of both Cd and Hg as individual and combined. Hepatotoxicity was evaluated by monitoring the biochemical parameters of the liver and their accumulation in the liver as well as therapeutic role of vitamin C in said toxicity in rabbits (Oryctolagus cuniculus). In this research, cadmium chloride (1.5 mg/kg), mercuric chloride (1.2 mg/kg), and vitamin C (150 mg/kg of body weight) were orally administered to treatment groups of the rabbits for 28 alternative days. Various biochemical parameters of the liver such as lactate dehydrogenase (LDH), aspartate aminotransferase (ASAT), bilirubin, alanine aminotransferase (ALAT), total protein, and gamma glutamyl transferase (GGT) were estimated using blood samples. Some biochemical parameters like ASAT, ALAT, LDH, GGT, and bilirubin were significantly elevated (P ≤ 0.001) in individual Cd and Hg treatment groups, while the level of total protein was found to be significantly declined. The effects of Cd and Hg in the presence of vitamin C on these biochemical parameters were low as compared to metals-treated groups. Similar results were found when rabbits were treated with co-administration of both metals and vitamin C. Accumulation of Cd and Hg found to be higher in the liver. However, chemoprevention and chemotreatment with vitamin C significantly (P ≤ 0.01) minimized the toxicological effects of both metals but not regained the accumulation similar to that of the control group. The findings of this study provide awareness on accumulation of metals in the liver in rabbits and their toxicity tested through biochemical parameters as well as the therapeutic role of vitamin C in such alterations.

Estimated exposure to mercury from fish consumption among women anglers of childbearing age in the Great Lakes region

Women of childbearing age (WCBA) are advised by state, tribal, and federal agencies to limit their consumption of certain fish, in part, because of concerns about the ingestion of methylmercury and its impact on the development of fetuses. We studied the fish-eating habits of WCBA who had a fishing license and lived near the Great Lakes, where mercury in locally-caught fish is a concern, as these women were likely at greater risk of elevated mercury exposure than the general population. We used a web-based diary method to gather fish consumption data from WCBA anglers over a 4-month period in the summer of 2014. We estimated mercury intake based on reported mercury content of species consumed, frequency of consumption, and meal portion size, and calculated percent exceeding the USEPA reference dose (RfD). Based on these calculations, we estimated that study participants (n = 1395) ingested 0.031 ± 0.002 (95% CI) ug/kg/d of methylmercury (arithmetic mean). We also found that 3.4% of study participants exceeded the RfD when we averaged estimated intake over the 4-month study period. While most (82%) of the fish meals WCBA anglers ate were purchased fish meals generally low in mercury, study participants ingested a disproportionate amount of mercury from locally-caught fish meals (18% of meals contributed 37% of mercury intake). We estimated 11% of WCBA anglers who did not follow state and federal guidelines in effect at the time of our study exceeded the mercury RfD, whereas fewer than 1% of WCBA anglers who followed the guidelines exceeded the RfD. These findings highlight the importance of encouraging WCBA to follow guidelines from agencies for locally-caught fish, in combination with guidelines for purchased fish.

Current Level of Fish Consumption is Associated with Mortality in Chinese but not US Adults: New Findings From Two Nationwide Cohort Studies With 14 and 9.8 Years of Follow-Up

SCOPE

Whether dietary fish consumption is linked to mortality remains unclear. We aim to investigate the association of fish consumption with mortality in Chinese and US nationwide populations.

METHODS AND RESULTS

We utilize data from China Health and Nutrition Survey (CHNS, n = 14 117) and National Health and Nutrition Examination Survey (NHANES, n = 33 221) including NHANES III conducted in 1988-1994 and continuous NHANES 1999-2010. Cox proportional hazards regression is used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). During a median follow-up of 14 and 9.8 years for CHNS and NHANES, 1007 and 5209 deaths are documented, respectively. Among Chinese adults, increased fish intake is significantly associated with decreased total mortality. The multivariable-adjusted HRs (95% CIs) across increasing categories of fish intake are 0.45 (0.36-0.56), 0.72 (0.60-0.86), and 0.70 (0.59-0.85) (p trend < 0.0001). However, fish intake is not associated with total mortality among US adults (p trend = 0.21). We only detected a borderline inverse association between fish intake and stroke mortality (p trend = 0.05), whereas a positive association with diabetes mortality in the third category of fish intake in NHANES.

CONCLUSION

In these two nationwide cohort studies, fish consumption is associated with a reduced risk of total mortality for Chinese but not US populations.

Association of methylmercury intake from seafood consumption and blood mercury level among the Asian and Non-Asian populations in the United States

BACKGROUND

MeHg is a well-established neurotoxicant for fetal brain growth and development and has been shown to increase the risk of cardiovascular disease in aging populations. In the U.S., Asian populations are of particular concern because of their seafood consumption behaviors.

OBJECTIVES

Our objective was to calculate the average daily MeHg intake (ADMI) from seafood and to assess the relationship between ADMI with blood methylmercury (BMeHg) concentrations, specifically among women of reproductive age (WORA) and adults ≥ 50 years of age.

METHODS

We estimated ADMI from seafood using the 30-day fish consumption data from the NHANES 2011-2014 datasets. Using multivariable linear regression, we estimated the proportional change in mean BMeHg associated with a doubling of the ADMI. Further, correlations between ADMI and BMeHg were compared between Asians and other racial/ethnic groups.

RESULTS

Our analysis found both Asian WORA and Asian adults age ≥ 50 years old had significantly higher BMeHg levels and ADMI than their Non-Asian counterparts. Correlations between ADMI from seafood and blood Hg levels were stronger among Asian WORA than among Non-Asian WORA. Key fish species that influenced the dietary MeHg intake for Asians were mackerel, tuna, and "other known/unknown fish species".

CONCLUSION

We confirmed that Asian populations have higher MeHg intake than the Non-Asian population in the U.S. and seafood intake is a key predictor of blood Hg concentration, especially among Asian women of reproductive age. Future studies should incorporate information on other known and unknown fish species that are frequently consumed by Asian populations and different parts and fish organs eaten to better understand determinants of MeHg exposure.

Results of a national survey of high-frequency fish consumers in the United States

Exposure to contaminants in fish may be associated with adverse health outcomes even as fish consumption is generally considered beneficial. Risk assessments conducted to support regulatory analyses rely on quantitative fish consumption estimates. Here we report the results of a national survey of high-frequency fish consumers (n = 2099) based on a survey population statistically representative of ~17.6 million U.S. individuals consuming three or more fish meals per week. The survey was conducted during 2013 using an on-line survey instrument. Total fish consumption averaged 111g/day from market, restaurant and self-caught sources. Depending on the season, the incidence of individuals reporting consumption of self-caught species ranged between 10-12% of our high-frequency fish consuming demographic, averaging approximately 30g/day and comprising 23% of total fish consumption from all sources of fish. Recreational or self-caught consumption rates vary regionally and are poorly understood, particularly for high-frequency consumers, making it difficult to support national-scale assessments. A divergence between sport-fishing and harvesting of fish as a food-staple is apparent in survey results given differences in consumption patterns with income and education. Highest consumption rates were reported for low income respondents more likely to harvest fish as a food staple. By contrast, the incidence of self-caught fish consumption was higher with income and education although overall consumption rates were lower. Regional differences were evident, with respondents from the East-South Central and New England regions reporting lowest consumption rates from self-caught fish on the order of 12-16g/day and those from Mountain, Pacific and Mid-Atlantic regions reporting highest rates ranging from 44 to 59g/day. Respondent-specific consumption rates together with national-level data on fish tissue concentrations of PCBs, MeHg, and PFOS suggest that 10-58% of respondents reporting self-caught fish consumption are exposed to concentrations of these contaminants that exceed threshold levels for health effects based on a target hazard index of one, representing 2.3M to 19M individuals. The results of this nationwide survey of high-frequency fish consumers highlights regional and demographic differences in self-caught and total fish consumption useful for policy analysis with implications for distributional differences in potential health impacts in the context of both contaminant exposures as well as protective effects.

Correlations of Biomarkers and Self-Reported Seafood Consumption among Pregnant and Non-Pregnant Women in Southeastern Louisiana after the Gulf Oil Spill: The GROWH Study

Seafood contains health-promoting fatty acids, but is often contaminated with mercury (Hg), complicating recommendations and choices around fish consumption during pregnancy. Self-reported diet may be subject to inaccuracy and this inaccuracy could differ according to pregnancy status. We investigated correlations between self-reported seafood consumption and blood levels of Hg and n-3 polyunsaturated fatty acids (PUFAs) in women affected by the Deepwater Horizon oil spill. Spearman correlation coefficients were calculated comparing log blood Hg and n-3 PUFAs to seafood consumption, then stratified by pregnancy status. Crude and adjusted linear regression models were constructed using biomarkers of Hg and n-3 PUFA and seafood consumption, adjusting for age and pregnancy status. Weak but significant correlations were found between log Hg levels and intake of Hg-containing seafood ( r = 0.15) and were slightly stronger among pregnant women ( r = 0.22, vs. r = 0.10). Biomarkers for n-3 PUFAs were significantly correlated with seafood consumption ( r = 0.12). Hg-containing seafood consumption was associated with increased blood level Hg in the highest quartile in both unadjusted (β = 0.34, 95% CI: 0.15-0.53) and adjusted models (β = 0.28, 95% CI: 0.08-0.48). Self-reported seafood consumption was correlated with biomarkers of both n-3 PUFA and Hg, but this association was different when stratified by pregnancy status. Pregnant women may have better recall of Hg-containing seafood compared to nonpregnant women.

Blood mercury concentrations are associated with decline in liver function in an elderly population: a panel study

BACKGROUND

Mercury is a toxic heavy metal and is known to affect many diseases. However, few studies have examined the effects of mercury exposure on liver function in the general population. We examined the association between blood mercury concentrations and liver enzyme levels in the elderly.

METHODS

We included 560 elderly participants (60 years or older) who were recruited from 2008 to 2010 and followed up to 2014. Subjects visited a community welfare center and underwent a medical examination and measurement of mercury levels up to five times. Analyses using generalized estimating equations model were performed after adjusting for age, sex, education, overweight, alcohol consumption, smoking, regular exercise, high-density lipoproteins cholesterol, and total calorie intake. Additionally, we estimated interaction effects of alcohol consumption with mercury and mediation effect of oxidative stress in the relationship between mercury levels and liver function.

RESULTS

The geometric mean (95% confidence interval (CI)) of blood mercury concentrations was 2.81 μg/L (2.73, 2.89). Significant relationships were observed between blood mercury concentrations and the level of liver enzymes, including aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma glutamyl transferase (GGT), after adjusting for potential confounders (P < 0.05). The odds ratios of having abnormal ALT levels were statistically significant in the highest mercury quartile compared to those with the lowest quartile. Particularly, regular alcohol drinkers showed greater effect estimates of mercury on the liver function than non-drinkers groups. There was no mediation effect of oxidative stress in the relationship between blood mercury concentrations and liver function.

CONCLUSIONS

Our results suggest that blood mercury levels are associated with elevated liver enzymes and interact with alcohol consumption for the association in the elderly.

Childhood and adolescent fish consumption and adult neuropsychological performance: An analysis from the Cape Cod Health Study

OBJECTIVE

This exploratory analysis examines the relationship between childhood and adolescent fish consumption and adult neuropsychological performance.

DESIGN

Data from a retrospective cohort study that assessed fish consumption from age 7 to 18years via questionnaire were analyzed. A subset of the population underwent domain-specific neuropsychological assessment. Functions evaluated included omnibus intelligence, academic achievement, language, visuospatial skills, learning and memory, attention and executive function, fine motor coordination, mood, and motivation to perform.

SETTING

Eight towns in the Cape Cod region of Massachusetts, USA, an area characterized by high fish consumption and an active seafood industry.

SUBJECTS

A cohort of 1245 subjects was recruited based on Massachusetts birth records from 1969 to 1983. Sixty-five participants from the original cohort underwent neuropsychological testing in adulthood (average age=30years).

RESULTS

Participant report of consuming fish at least twice per month was associated with better performance on tests of visual learning, memory, and attentional abilities. However, self-report of consuming fish at rates higher than twice per month was not associated with improved abilities. No statistically significant associations were observed between type of fish consumed (e.g., species known to be high in methylmercury content) and test outcomes.

CONCLUSIONS

The results suggest that moderate fish consumption during childhood and adolescence may be associated with some cognitive benefits and that consumption of fish during this exposure window may potentially influence adult neuropsychological performance. Future prospective studies should take into account this time period of exposure.

Regional and temporal trends in blood mercury concentrations and fish consumption in women of child bearing Age in the united states using NHANES data from 1999-2010

BACKGROUND

The primary route of exposure to methylmercury (MeHg), a known developmental neurotoxicant, is from ingestion of seafood. Since 2004, women of reproductive age in the U.S. have been urged to eat fish and shellfish as part of a healthy diet while selecting species that contain lower levels MeHg. Yet few studies have examined trends in MeHg exposure and fish consumption over time in this group of women with respect to their geographical location in the U.S.

METHODS

Data from six consecutive cycles of the National Health and Nutrition Examination Survey (NHANES), 1999-2010 (n = 9597) were used to determine trends in blood mercury for women aged 16-49 residing in different regions in the US, and according to age, race/ethnicity, income level, and fish consumption using geographic variables.

RESULTS

Overall, mean blood mercury concentrations differed across survey cycles and mercury concentrations were lower in 2009-2010 compared to 1999-2000. There were regional patterns in fish consumption and blood Hg concentrations with women living in coastal regions having the highest fish consumption in the past 30 days and the highest blood Hg levels compared to women residing inland.

CONCLUSIONS

On average, U.S. women of reproductive age were consuming more fish and blood mercury levels were lower in 2009-2010 compared to 1999-2000. However, efforts to encourage healthy fish consumption may need to be tailored to different regions in the U.S. given the observed spatial variability in blood mercury levels.

Transcriptomic characterization of zebrafish larvae in response to mercury exposure

Mercury is a widespread toxicant in aquatic environment that can cause deleterious effects on fish. Although a number of mercury-regulated genes have been investigated in adult fish, the transcriptional responses of fish larvae to acute mercury exposure are not well understood. In this study, RNA sequencing was used to examine the transcriptional changes in developing zebrafish larvae under a low concentration of mercuric chloride exposure from 24 to 120hpf. Our initial results showed that a total of 142.59 million raw reads were obtained from sequencing libraries and about 86% of the processed reads were mapped to the reference genome of zebrafish. Differential expression analysis identified 391 up- and 87 down-regulated genes. Gene ontology enrichment analysis revealed that most of the differential expressed genes are closely related to the regulation of cellular process, metabolic process, multicellular organismal process, biological regulation, pigmentation, and response to stimulus. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis demonstrated that antigen processing and presentation was the most significantly enriched pathway. Moreover, we characterized a novel and sensitive mercury-induced ABCB (ATP- binding cassette B subfamily) transporter gene - abcb5. This gene is localized on zebrafish chromosome 16 and contains a 4014bp open-reading frame. The deduced polypeptide is composed of 1337 amino acids and possesses most of functional domains and critical residues defined in human and mouse ABCB5/Abcb5. Functional analysis in vitro demonstrated that overexpression of zebrafish abcb5 gene can significantly decrease the cytotoxicity of mercury in LLC-PK1 cells, implying it is a potential efflux transporter of mercury. Thus, these findings provide useful insights to help further understand the transcriptional response and detoxification ability of zebrafish larvae following acute exposure to mercury.

Scientific foundations of fish-consumption advice for pregnant women: Epidemiological evidence, benefit-risk modeling, and an integrated approach

BACKGROUND

Pregnant women need fish consumption advice that increases seafood intake and simultaneously reduces methylmercury (MeHg) exposure. Two disciplines, epidemiology and benefit-risk modeling, can support such advice. Some current models suggest that fish consumption during pregnancy has only net beneficial effects. In contrast, many recent epidemiological studies have associated adverse effects on cognitive development with ordinary fish intake and MeHg doses routinely encountered by up to one in six US women of childbearing age. Proposed federal fish-consumption advice is based solely on a benefit-risk model. A more complete assessment integrating both types of evidence is needed.

OBJECTIVES AND METHODS

The goal of this paper is to use a model to rank seafood items by their relative benefits and risks, producing consumer seafood choice recommendations that are also consistent with epidemiological observations. Recent epidemiological studies and benefit-risk models are reviewed, and model results are compared with one another and with epidemiological observations to identify commonalities that support inter-calibration.

RESULTS AND CONCLUSIONS

Both approaches quantify MeHg doses at which harm slightly exceeds benefit. A model from the US Food and Drug Administration (FDA) predicts adverse effects at fish intakes containing, on average, more than 16 times the the US Reference Dose (RfD) for MeHg. Epidemiological results indicate that the RfD itself approximates a minimal adverse dose. This conceptual similarity allows FDA's model to be calibrated with the epidemiological results to generate fish intake recommendations that both the model and the epidemiology suggest should have substantially positive public health impacts.

Associations of blood mercury, inorganic mercury, methyl mercury and bisphenol A with dental surface restorations in the U.S. population, NHANES 2003-2004 and 2010-2012

The potential adverse health effects of mercury from amalgam and bisphenol A (BPA) from composite resin have been significant concerns. It is unclear whether dental restorative materials significantly contribute to mercury or BPA levels. The purpose of this study is to use NHANES data including 14,703 subjects (2003-2004: n=7514; 2011-2012: n=7189) to examine the association between Dental Surface Restorations (DSR) and blood total mercury (THg), inorganic mercury (IHg), methyl mercury (MeHg) and urinary BPA through the stratification of covariates and multivariate analysis. Subjects were divided into three groups based on the number of dental surface restorations (DSRs, 0, 1-8, >8). Blood THg and IHg in 2003-2004 were significantly higher in the subjects with DSR (geometric mean of 0.48, 0.69 and 1.17μg/l for THg; 0.32, 0.33 and 0.39μg/l for IHg with DSR 0, 1-8 and >8). Similarly, increases of THg, IHg and MeHg were also observed in 2013-2014 (geometric mean of 0.51, 0.69 and 0.99μg/l for THg; 0.40, 0.49 and 0.66μg/l for MeHg; 0.20, 0.22 and 0.29μg/l for IHg with DSR 0, 1-8 and >8). Linear regression model analysis revealed blood THg and IHg in 2003-2004 and THg, IHg and MeHg in 2011-2012 were quantitatively associated with the number of DSRs. A dramatic decrease in urinary BPA from 2003 to 2004-2011-2012 was observed, but no significant increase with DSRs in either period of study. In conclusion, significant increases in blood THg, IHg, and MeHg in the subjects with DSRs are confirmed in a nationally representative population, a critical step in assessing the potential risk of adverse effects from dental restorative materials, but no association between dental fillings and urinary BPA was found.

Evaluating the effectiveness of the Minamata Convention on Mercury: Principles and recommendations for next steps

The Minamata Convention on Mercury is a multilateral environmental agreement that obligates Parties to reduce or control sources of mercury pollution in order to protect human health and the environment. The Convention includes provisions on providing technical assistance and capacity building, particularly for developing countries and countries with economies in transition, to promote its effective implementation. Evaluating the effectiveness of the Convention (as required by Article 22) is a crucial component to ensure that it meets this objective. We describe an approach to measure effectiveness, which includes a suite of short-, medium-, and long-term metrics related to five major mercury control Articles in the Convention, as well as metrics derived from monitoring of mercury in the environment using select bioindicators, including people. The use of existing biotic Hg data will define spatial gradients (e.g., biological mercury hotspots), baselines to develop relevant temporal trends, and an ability to assess risk to taxa and human communities of greatest concern. We also recommend the development of a technical document that describes monitoring options for the Conference of Parties, to provide science-based standardized guidelines for collecting relevant monitoring information, as guided by Article 19.

Cadmium and mercury exposure over time in Swedish children

PURPOSE

Knowledge about changes in exposure to toxic metals over time remains very sparse, in particular for children, the most vulnerable group. Here, we assessed whether a reduction in environmental pollution with cadmium (Cd) and mercury (Hg) caused a change in exposure over time. In total, 1257 children (age 4-9) in two towns in Sweden were sampled once in 1986-2013. Blood concentrations of Cd (b-Cd; n=1120) and Hg (b-Hg; n=560) were determined.

RESULTS

The median b-Cd was 0.10 (geometric mean 0.10; range 0.010-0.61) μg/L and b-Hg was 0.91 (geometric mean 0.83; range 0.021-8.2) μg/L. Children living close to a smelter had higher b-Cd and b-Hg than those in urban and rural areas. There was no sex difference in b-Cd or b-Hg, and b-Cd and b-Hg showed no significant accumulation by age. b-Cd decreased only slightly (0.7% per year, p<0.001) over the study period. In contrast, b-Hg did show a clear decrease over the study period (3% per year, p<0.001).

CONCLUSIONS

The exposure to Cd was very low but still might increase the risk of disease later in life. Moreover, b-Cd only showed a minor decrease, indicating that Cd pollution should be further restricted. b-Hg was relatively low and decreasing, probably because of reduced use of dental amalgam and lower Hg intake from fish. The b-Cd and b-Hg levels decreased much less than the levels of lead in the blood as previously found in the same children.

Quantitative analyses of the hepatic proteome of methylmercury-exposed Atlantic cod (Gadus morhua) suggest oxidative stress-mediated effects on cellular energy metabolism

BACKGROUND

Methylmecury (MeHg) is a widely distributed environmental pollutant with considerable risk to both human health and wildlife. To gain better insight into the underlying mechanisms of MeHg-mediated toxicity, we have used label-free quantitative mass spectrometry to analyze the liver proteome of Atlantic cod (Gadus morhua) exposed in vivo to MeHg (0, 0.5, 2 mg/kg body weight) for 2 weeks.

RESULTS

Out of a toltal of 1143 proteins quantified, 125 proteins were differentially regulated between MeHg-treated samples and controls. Using various bioinformatics tools, we performed gene ontology, pathway and network enrichment analysis, which indicated that proteins and pathways mainly related to energy metabolism, antioxidant defense, cytoskeleton remodeling, and protein synthesis were regulated in the hepatic proteome after MeHg exposure. Comparison with previous gene expression data strengthened these results, and further supported that MeHg predominantly affects many energy metabolism pathways, presumably through its strong induction of oxidative stress. Some enzymes known to have functionally important oxidation-sensitive cysteine residues in other animals are among the differentially regulated proteins, suggesting their modulations by MeHg-induced oxidative stress. Integrated analysis of the proteomics dataset combined with previous gene expression dataset showed a more pronounced effect of MeHg on amino acid, glucose and fatty acid metabolic pathways, and suggested possible interactions of the cellular energy metabolism and antioxidant defense pathways.

CONCLUSIONS

MeHg disrupts mainly redox homeostasis and energy generating metabolic pathways in cod liver. The energy pathways appear to be modulated through MeHg-induced oxidative stress, possibly mediated by oxidation sensitive enzymes.

Trends in Exposure to Chemicals in Personal Care and Consumer Products

Synthetic organic chemicals can be used in personal care and consumer products. Data on potential human health effects of these chemicals are limited-sometimes even contradictory-but because several of these chemicals are toxic in experimental animals, alternative compounds are entering consumer markets. Nevertheless, limited information exists on consequent exposure trends to both the original chemicals and their replacements. Biomonitoring (measuring concentrations of chemicals or their metabolites in people) provides invaluable information for exposure assessment. We use phthalates and bisphenol A-known industrial chemicals-and organophosphate insecticides as case studies to show exposure trends to these chemicals and their replacements (e.g., other phthalates, non-phthalate plasticizers, various bisphenols, pyrethroid insecticides) among the US general population. We compare US trends to national trends from Canada and Germany. Exposure to the original compounds is still prevalent among these general populations, but exposures to alternative chemicals may be increasing.

Results of micronucleus assays with individuals who are occupationally and environmentally exposed to mercury, lead and cadmium

Millions of humans are exposed occupationally and environmentally to lead, mercury and cadmium compounds. Mercury compounds are less abundant but some of them belong to the most toxic chemicals which are known. We evaluated the literature to find out if these metals act in humans as genotoxic carcinogens and if their health effects can be predicted by use of micronucleus (MN) assays with lymphocytes and/or with other genotoxicity tests. Numerous studies showed that lead and mercury induce cancer in humans and also in animals, in vitro experiments with cultured cells indicate that they cause DNA damage via different molecular mechanisms including release of reactive oxygen species and interactions with DNA repair processes. Also in most human studies, positive results were obtained in MN tests with lymphocytes (all 15 occupational studies with lead yielded positive results, with mercury 6 out of 7 investigations were positive). For cadmium, there is clear evidence that it causes cancer in humans; however, induction of chromosomal damage was only seen in high dose experiments with mammalian cells while results of animal and human studies yielded conflicting results (only in 2 of 5MN trials with humans positive findings were reported). Possibly, non-genotoxic mechanisms such as inhibition of apoptosis and interaction with signaling pathways account for the carcinogenic properties of cadmium species. The findings of MN studies with lead and mercury are in excellent agreement with results which were obtained with other endpoints (e.g. chromosomal aberrations and comet formations) and it is evident that this approach can be used for occupational and environmental monitoring of exposed individuals. Important future tasks will be the realization of larger studies with a uniform standardized protocol, the additional evaluation of anomalies other than MN (nuclear buds and bridges) and the combination of such trials with investigations which allow to define the molecular mechanisms relevant for exposed humans.

Human exposure to methylmercury from crayfish (Procambarus clarkii) in China

Methylmercury (MeHg) accumulation in aquatic food raises global concerns about human exposure to MeHg. Crayfish is the world's third largest farmed crustacean species and a favorite aquatic food in many countries. However, human health hazard due to MeHg exposure via crayfish consumption is unclear, partly because appropriate survey data are lacking. We report on mercury concentrations and speciation in edible tail muscle of crayfish collected from restaurants in 23 Chinese cities. On average, MeHg constituted 99.1 % of mercury in tail muscle, and MeHg concentrations were comparable with those reported for fish in China. Variation in MeHg concentrations was not attributable to broad geographic region (i.e., provinces) or tail length. For different populations, potential health risk (characterized by hazard quotient or HQ) of MeHg exposure through crayfish consumption depended largely on crayfish consumption rates. In particular, a health hazard (HQ > 1) was found for high-rate consumers (i.e., 95 %ile or higher) in some cities in the middle and lower reaches of the Yangtze River (MLYR), during the peak consumption season. Our results suggest that more attention should be paid to dietary MeHg intake via crayfish consumption in China, particularly for communities with high consumption in MLYR.

Suboptimal Plasma Long Chain n-3 Concentrations are Common among Adults in the United States, NHANES 2003-2004

Population data on long-chain omega-3 polyunsaturated fatty acid (LCn-3 PUFA) status from biomarkers of dietary intake is lacking. The objectives were to describe plasma LCn-3 PUFA concentrations and compare them to concentrations associated with cardiovascular health and dietary recommendations for two servings of seafood/week. Fasting plasma fatty acids were measured among 1386 subjects ≥20 years from the National Health and Nutrition Examination Survey, 2003–2004. LCn-3 concentrations represent the sum of eicosapentaenoic acid, docosapentaenoic acid and docosahexaenoic acid relative to total fatty acids (expressed as a percentage). Mean LCn-3 PUFA concentration was 2.07% (95% CI 1.95–2.19). Overall, 80.6% of participants had LCn-3 below concentrations recommended for cardiovascular health. Hispanic participants were the most likely to have LCn-3 PUFA below recommended levels. Nearly all participants (95.7%) had LCn-3 below concentrations associated with cardiovascular protection. Older participants (≥60 years) had higher LCn-3 PUFA concentrations than those aged 20–39 years but not aged 40–59 years. LCn-3 PUFA concentrations were lower for Hispanic participants relative to non-Hispanic black participants. Suboptimal LCn-3 concentrations are common among U.S. adults. These findings highlight the need to increase LCn-3 intake among Americans.

Parenteral nutrition as an unexpected and preventable source of mercury exposure in preterm infants

Perinatal mercury exposure has neurodevelopmental consequences, which may be worse in preterm infants. In our cohort (N = 60), maternal and infant prenatal exposures were low, but infant levels increased during hospitalization and correlated only with duration of parenteral nutrition. A non-negligible exposure resulted from the nutrition preparation on equipment shared with adult preparations.

Umbilical cord blood and placental mercury, selenium and selenoprotein expression in relation to maternal fish consumption

Seafood is an important source of nutrients for fetal neurodevelopment. Most individuals are exposed to the toxic element mercury through seafood. Due to the neurotoxic effects of mercury, United States government agencies recommend no more than 340g (12oz) per week of seafood consumption during pregnancy. However, recent studies have shown that selenium, also abundant in seafood, can have protective effects against mercury toxicity. In this study, we analyzed mercury and selenium levels and selenoprotein mRNA, protein, and activity in placenta of a cohort of women in Hawaii in relation to maternal seafood consumption assessed with dietary surveys. Fish consumption resulted in differences in mercury levels in placenta and cord blood. When taken as a group, those who consumed no fish exhibited the lowest mercury levels in placenta and cord blood. However, there were numerous individuals who either had higher mercury with no fish consumption or lower mercury with high fish consumption, indicating a lack of correlation. Placental expression of selenoprotein mRNAs, proteins and enzyme activity was not statistically different in any region among the different dietary groups. While the absence of seafood consumption correlates with lower average placental and cord blood mercury levels, no strong correlations were seen between seafood consumption or its absence and the levels of either selenoproteins or selenoenzyme activity.

60-Day chronic exposure to low concentrations of HgCl2 impairs sperm quality: hormonal imbalance and oxidative stress as potential routes for reproductive dysfunction in rats

Mercury is a toxic and bio-accumulative heavy metal of global concern. While good deals of research have been conducted on the toxic effects of mercury, little is known about the mechanisms involved in the pathogenesis of male reproductive dysfunction induced by mercury. Therefore, the purpose of this study was to assess the effects and underlying mechanisms of chronic mercury exposure at low levels on male reproductive system of rats. Three-month-old male Wistar rats were divided into two groups and treated for 60 days with saline (i.m., Control) and HgCl2 (i.m. 1st dose: 4.6 µg/kg, subsequent doses 0.07 µg/kg/day). We analyzed sperm parameters, hormonal levels and biomarkers of oxidative stress in testis, epididymis, prostate and vas deferens. Mercury treatment decreased daily sperm production, count and motility and increased head and tail morphologic abnormalities. Moreover, mercury treatment decreased luteinizing hormone levels, increased lipid peroxidation on testis and decreased antioxidant enzymes activities (superoxide dismutase and catalase) on reproductive organs. Our data demonstrate that 60-day chronic exposure to low concentrations of HgCl2 impairs sperm quality and promotes hormonal imbalance. The raised oxidative stress seems to be a potential mechanism involved on male reproductive toxicity by mercury.

Total and methyl mercury in whole blood measured for the first time in the U.S. population: NHANES 2011-2012

BACKGROUND

Despite the public health and toxicologic interest in methyl mercury (MeHg) and ethyl mercury (EHg), these mercury species have been technically difficult to measure in large population studies.

METHODS

Using NHANES 2011-2012 data, we calculated reference ranges and examined demographic factors associated with specific mercury species concentrations and the ratio of MeHg to THg. We conducted several multiple regression analyses to examine factors associated with MeHg concentrations and also with the ratio of MeHg to THg.

RESULTS

Asians had the highest geometric mean concentrations for MeHg, 1.58 µg/L (95% CI 1.29, 1.93) and THg, 1.86 µg/L (1.58, 2.19), followed by non-Hispanic blacks with MeHg, 0.52 µg/L (0.39, 0.68) and THg, 0.68 µg/L (0.54, 0.85). Greater education attainment in adults and male sex were associated with higher MeHg and THg concentrations. Race/ethnicity, age, and sex were significant predictors of MeHg concentrations, which increased with age and were highest in Asians in all age categories, followed by non-Hispanic blacks. Mexican Americans had the lowest adjusted MeHg concentrations. The ratio of MeHg to THg was highest in Asians, varied by racial/ethnic group, and increased with age in a non-linear fashion. The amount of increase in the MeHg to THg ratio with age depended on the initial ratio, with a greater increase as age increased. Of the overall population, 3.05% (95% CI 1.77, 4.87) had MeHg concentrations >5.8 µg/L (a value that corresponds to the U.S. EPA reference dose). The prevalence was highest in Asians at 15.85% (95% CI 11.85, 20.56), increased with age, reaching a maximum of 9.26% (3.03, 20.42) at ages 60-69 years. Females 16-44 years old had a 1.76% (0.82-3.28) prevalence of MeHg concentrations >5.8 µg/L.

CONCLUSIONS

Asians, males, older individuals, and adults with greater educational attainment had higher MeHg concentrations. The ratio of MeHg to THg varied with racial/ethnic group, increased with age, and was nonlinear. U.S. population reference values for MeHg and the ratio of MeHg to THg can assist in more precise assessment of public health risk from MeHg consumed in seafood.

TrkB overexpression in mice buffers against memory deficits and depression-like behavior but not all anxiety- and stress-related symptoms induced by developmental exposure to methylmercury

Developmental exposure to low dose of methylmercury (MeHg) has a long-lasting effect on memory and attention deficits in humans, as well as cognitive performance, depression-like behavior and the hippocampal levels of the brain-derived neurotrophic factor (Bdnf)in mice. The Bdnf receptor TrkB is a key player of Bdnf signaling. Using transgenic animals, here we analyzed the effect of the full-length TrkB overexpression (TK+) on behavior impairments induced by perinatal MeHg. TK overexpression in the MeHg-exposed mice enhanced generalized anxiety and cue memory in the fear conditioning (FC) test. Early exposure to MeHg induced deficits in reversal spatial memory in the Morris water maze (MWM) test and depression-like behavior in the forced swim test (FST) in only wild-type (WT) mice but did not affect these parameters in TK+ mice. These changes were associated with TK+ effect on the increase in Bdnf 2, 3, 4 and 6 transcription in the hippocampus as well as with interaction of TK+ and MeHg factors for Bdnf 1, 9a and truncated TrkB.T1 transcripts in the prefrontal cortex. However, the MeHg-induced anxiety-like behavior in the elevated plus maze (EPM) and open field (OF) tests was ameliorated by TK+ background only in the OF test. Moreover, TK overexpression in the MeHg mice did not prevent significant stress-induced weight loss during the period of adaptation to individual housing in metabolic cages. These TK genotype-independent changes were primarily accompanied by the MeHg-induced hippocampal deficits in the activity-dependent Bdnf 1, 4 and 9a variants, TrkB.T1, and transcripts for important antioxidant enzymes glyoxalases Glo1 and Glo2 and glutathione reductase Gsr. Our data suggest a role of full-length TrkB in buffering against memory deficits and depression-like behavior in the MeHg mice but propose the involvement of additional pathways, such as the antioxidant system or TrkB.T1 signaling, in stress- or anxiety-related responses induced by developmental MeHg exposure.